These findings suggest changes are needed in the current preschool approach, with federally-funded programs mostly populated by students from lower-income families, while private programs serve children from more affluent families. The often vast vocabulary gap between low-income and middle- or high-income students has been tied to lower academic achievement and higher illiteracy rates later in life.

Researchers found that preschoolers saw a more dramatic improvement in their language skills when they were grouped in classrooms with high-skills students. Meanwhile children who began school with higher language assessment scores were in no way negatively affected by learning alongside low-skills students.

What implications could this have for education policy and teaching literacy? “It might mean that classroom composition is affecting growth of language skill, even as much as the content and quality of instruction,” Laura M. Justice, one of the study’s authors and an education professor at Ohio State University told Early Ed Watch. “Policymakers need to think very seriously about how preschool classrooms are composed.”